The present invention relates to a radio communication system for transmitting and receiving divided pieces of data in different transmission paths simultaneously, and particularly to a communication system, a transmitting apparatus, a receiving apparatus, a processing method in the apparatus, and a program for making a computer carry out the method.
A frequency diversity system is a method of transmitting an identical signal on a plurality of different carriers and selecting or synthesizing them on a receiving side to thereby improve characteristics. The frequency diversity system has an advantage in that since an identical signal is transmitted on a plurality of carriers, even when some of the carriers cannot be received, the signal can be received on another carrier. The frequency diversity system is widely used, particularly for an OFDM (Orthogonal Frequency Division Multiplexing) system, which has many carriers, because there is an extremely low possibility that none of the carriers can be received and a combination of carriers for transmitting an identical signal can be selected flexibly (see, for example, Japanese Patent Laid-Open No. 2000-201130 (FIG. 5) and Japanese Patent Laid-Open No. Hei 10-336159 (FIG. 1)).
Since the frequency diversity system described above transmits an identical signal on a plurality of carriers, even when a dip phenomenon occurs, in which the received radio field intensity is decreased by carriers of a direct wave and a delayed wave in opposite phase with each other on a receiving side due to multipath effects, for example, the signal can be received on one of the carriers.
However, since the identical signal is transmitted simultaneously, the frequency diversity system correspondingly lowers the transmission rate. With current technology, a maximum radio transmission speed in the IEEE802.11a standard by a working group of an IEEE (Institute of Electrical and Electronics Engineers) 802 standardization committee, for example, is 54 Mbps (bits/second), which cannot be said to be sufficient as compared with wire transmission speeds.